1. Field of the Invention
The present invention relates generally to a mill for the production of continuous seam-welded tubes or pipes and, more particularly, to a system for changing such a mill from the production of tubes of one size or shape of tube to the production of tubes of another and different size or shape.
2. Description of the Prior Art
In accordance with a well known process for producing seam-welded tubes, a continuous strip or skelp is advanced through forming sections of a tube mill apparatus which includes a series of forming rolls. The strip is formed into a tubular form having an open, longitudinally extending seam formed by the abutting edges of strip being formed. The tubular form is then advanced through a welding section wherein the abutting edges are urged together and joined by a suitable welding process. The welding process may cause the formation of an unwanted bead which may next be removed by a suitable scarfing procedure. The welded tube is then after passing through a cooling zone, advanced through a series of sizing and squaring rollers whereby the tube is formed to the final configuration and size. The advancing continuous tube is then severed by means of a travelling cutting unit into individual sections of a predetermined length.
The tube forming apparatus is designed to be capable of conversion to the production of various sizes and cross-sectional configurations of tube. As will be readily manifest, such apparatus constitutes massive precision machines representing a considerable investment of capital. Heretofore, it was often necessary to shut down a production of tubes of one size or shape to convert the apparatus to produce tubes of a different size or shape. More specifically, the line was shut down and the various components were individually removed and replaced by components required for production of the next product. The replacement components then had to be properly set and adjusted on the line before production could resume. The entire changeover routine could consume a considerable period of time, as much as five or six hours or more. obviously, the changeover time involves a considerable expenditure in time and capital, and an extensive loss of production. As a result, it becomes necessary to maintain unduly large inventories of finished products, contrary to the current trend toward maintaining minimum inventory and frequently changing from the production of one product to another.
The aforementioned deficiencies were overcome by producing a tube mill of the type illustrated and described in U.S. Pat. No. 5,600,988 Nelson D. Abbey, III et al. The apparatus utilized in the aforementioned patent includes an automated procedure for exchanging components of the mill sections to change from production of tubes of one size or shape to the production of tubes of another and different size or shape. The stand assemblies of the mill to be changed during the changeover procedure are mounted on removable sub-base sections adapted to be carried on a fixed mill base. The stand assemblies and associated subbase may be removed from the fixed mill base and transferred to a remote wash station and thence to an off-line changeover location adjacent a secondary storage cart.
An automatically operated pressure fluid activated push-pull module pulls the front stand onto the secondary storage cart for temporary removal to a temporary storage area. Simultaneously, another secondary cart carrying empty roll racks is positioned along the roll stand assembly adjacent the exposed forming rolls and associated spacers. The push-pull module pushes the roll rack toward forming rolls and roll manipulators push the rolls and spacers onto the empty roll rack. The secondary storage cart carrying the removed forming rolls is moved to another position away from the stand assembly and eventually to a remote forming roll storage area. Another secondary storage cart with roll racks carrying the changeover rolls is indexed adjacent the roll stand assembly and the push-pull module pushes the roll rack toward the roll stand allowing the roll manipulators to be actuated to engage and pull the new forming rolls onto the roll stand assembly. The secondary cart with the emptied roll racks is moved toward the secondary forming roll storage cart exposing the newly positioned forming rolls.
The secondary front stand storage cart is indexed adjacent the roll stand assembly with the newly positioned forming rolls and the front stands are pushed into engagement with the roll stands and secured in place preparatory to being returned to the mill section for operation.
It will be appreciated that the advantages of a tube mill of the type alluded to above include less down time of the mill even for relatively short production runs.
The continuous tube mill incorporating the above concepts enables preventative maintenance and cleaning of the forming roll assemblies to be easily accomplished without disruption of production.
Since each of the primary sections of the mill are effectively independent of the other, each section may be of differing sophistication without adversely affecting the overall mill operation.
In most instances in the changeover systems of the prior art, the changeover modules include the forming rolls, the associated bearing blocks, the supporting spindles, and the adjustment mechanism. The transportation of particularly the spindles exposes the bearing surfaces to dirt, dust, and grime that tends to decrease the effective life cycle of the equipment. The cost of each module is considerably high. This is a result of the fact that each module is for all intents and purposes a complete forming station.